The invention is based on a drill bit for an air-cooled dry drilling method.
When drilling with drill bits, a distinction is made between purely rotary application, that is, drilling without vibration of the material to be drilled, and drilling with a percussive drilling tool, for example with a hammer drill. For the first-mentioned case, drill bits for working very hard rock are known, in which sintered diamond layers are arranged on the end face of the drill bit. These layers do not have any defined cutting edges but are permeated by a diamond granulation in a similar way as diamond grinding wheels. Material removal is therefore more of a grinding action than a cutting action. Moreover, drill bits having inserted carbide cutting elements have become known which remove material by percussive working, for example with a hammer drill.
The first-mentioned drill bit has the disadvantage that it can only be used with a stand, because of the low specific cutting force as a result of the large area, in order to achieve the requisite thrust force. This requires a high technical outlay on equipment and long setting-up times and therefore by and large involves high expenditure. The other drill bit mentioned, with carbide cutting elements, reaches its limits when working very hard rock, because carbide is substantially less hard than diamond.
With the known drill bits, a further disadvantage is that they are essentially operated with water cooling to cool the cutting area and remove the drilling dust. This also requires a high technical outlay on equipment and cannot easily be used in all applications.
Moreover, from the field of mining, especially coal mining, diamond tools have become known for drilling in the most diverse rock types and formations. For special application in soft to medium-hard formations such as salt, shale and anhydrite, etc., a drilling tool with PCD cutting elements (polycristalline, synthetic diamond coating) has become known which is fitted with annular cutting elements. The drilling conditions in mining are essentially quite different from conditions in building construction and civil engineering, so that no kind of ideas whatsoever can be gleaned here for the present invention.